Header position control with forward contour prediction

ABSTRACT

A system for harvester header height and tilt control includes a sensor, such as a crop edge detector, mounted on the harvester for predicting ground contour of an area a substantial distance in front of the header for generally the entire width of the header. An on-board processor calculates the desired header height and tilt for that area in advance of the harvester reaching the area. The early ground contour measurements enable faster and smoother header height adjustments requiring reduced hydraulic power. The predicted contour also facilitates early compensation for the effects of abrupt header attitude changes resulting from harvester ground wheels or tracks riding on that contour. The system can be used to maintain header height a preselected distance below the crop heads to reduce harvester throughput.

BACKGROUND OF THE INVENTION

The present invention relates generally to agricultural harvesters and,more specifically, to header height control for such harvesters.

A self-propelled harvester such as a combine usually includes a headerfor engaging a number of transversely spaced rows or a substantial widthof crop. To maintain the header at the desired level above the ground orbelow the crop heads for efficient harvesting and for header groundingavoidance, an automatic header height control system is provided whichtypically includes a mechanical feeler or an acoustic sensor or similarnon-contact ground sensing device mounted on the header. Examples ofpreviously available devices are shown in U.S. Pat. Nos. 6,173,614;5,704,200; 5,463,854; 5,155,984 and 4,171,606. U.S. Pat. No. 4,776,153shows a header height control system with a plurality of feelers and atilt control.

Although available control systems generally provide good positioncontrol in most situations and relieve the operator of the tedious jobof manually adjusting height or tilt with changing ground and cropconditions, several problems exist with the systems. Hydraulic powerrequirements and material stress levels often are high when the liftsystems are providing a fast response. The systems often fail to respondin time to avoid inefficient crop pickup, excessive crop materialintake, or grounding and damage of the header. System response time is aproblem when the harvester is travelling at relatively high speeds, suchas when operating in field conditions wherein crop yield is low, andwhen the harvester is operating in fields having substantial groundcontour changes. Tilt response time at high speeds or in fields withvery uneven surface contours is often too slow for headers havingautomatic tilting systems to maintain the header generally parallel tothe ground such as shown in the aforementioned U.S. Pat. No. 4,776,153.Header grounding and damage, and improper header operating height,result in decreased productivity. When the harvester is crossingdepressions such as valleys, gullies or swales, the header can begrounded and damaged before the lift system can respond to the suddenrise in the ground surface. Grounding is a particular problem when thefront harvester wheels are in a depression and the header is adjacent araised surface area. Near the apex of a hill or mounded area, the headeris often too high and misses crop since the system cannot respondquickly to the abrupt change in ground surface.

BRIEF SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved header position control system for a combine or otherharvester. It is a further object to provide such a control system whichovercomes most or all of the aforementioned problems.

It is another object of the invention to provide a header positioncontrol system having smoother response with reduced hydraulic powerrequirements and less material stress, particularly during high speedoperations in fields with abruptly changing ground contours, than atleast most previously available systems.

It is a further object to provide a header position control system for aharvester which reduces or eliminates the incidences of header over- orunder-height when depressions or rises in the ground surface areencountered. It is still another object of the invention to provide aheader position control system which predicts and compensates for theground irregularities encountered by the ground wheel support structureand the header.

It is another object to provide an improved harvester height controlsystem wherein desired header height and/or tilt position for a forwardlocation is calculated in advance of the header and any ground sensingtransducer on the header arriving at the location. It is still anotherobject to provide such a system which is complementary to anyconventional sensing transducer on the header and which can provide apredictive contour history over the entire width of the header.

It is yet a further object to provide an improved harvester positioncontrol system for maintaining cut height within a preselected range ofthe crop heads to reduce non-crop material throughput and increaseproductivity.

The system for improved header postition control includes a sensor, suchas a crop edge detector, mounted on the harvester for measuring groundcontour of an area a substantial distance in front of the header andproviding a surface profile indication over the whole platform width.The sensor includes a transmitter mounted on the harvester for radiatinga signal across an area approximately equal to the width of the path tobe traversed by the header, and a receiver which receives reflectedsignals. Travel times of the signals from a radiated area in the pathare utilized to estimate ground contour of that area. The ground contourcan be estimated directly by scanning the area with a crop penetratingsignal, such as a high frequency radar signal, and receiving reflectionsfrom the ground. By scanning with a laser device such as a rotatablecrop edge sensor, signals are reflected from the crop and provide a cropcontour signal. The crop contour signal can be used to maintain theheader a preselected distance below the crop heads to reduce throughputand increase harvester productivity. The crop contour signal can also beused to estimate ground surface profile.

An on-board processor calculates the desired header height and/or tiltfor an area in advance of the harvester reaching the area. The earlyground contour/crop contour measurements enable the height control andtilt control, if the combine is so equipped, to begin to makecorrections in advance of the header reaching the area for smootheradjustments with less stress on harvester components. Hydraulic powerrequirements and header reaction response time are reduced, featureswhich are particularly important when the harvester is operated atrelatively high speeds or in fields with abruptly changing groundsurface contours. The contour prediction may also used to compensate foreffects of header attitude changes resulting from harvester groundwheels or tracks riding on that contour.

These and other objects, features and advantages of the presentinvention will become apparent to one skilled in the art upon readingthe following detailed description in view of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a harvester with a header position controlsystem.

FIG. 2 is a schematic of a top view of the harvester of FIG. 1 operatingin a field.

FIGS. 3A and 3B are schematic representations of the harvester showingthe effects of ground contour on travel distance of a signal from theheader position control system transceiver.

FIG. 4 is a schematic representation of a transceiver and control systemutilized with the harvester of FIGS. 1-3.

FIG. 5 is a perspective view of a transceiver utilized with the controlsystem of FIG. 4.

FIG. 6 is a typical distance signal for a full header width scan.

FIG. 7 is a top view of a harvester showing the effect of slope on afull header width scan.

FIG. 8 is a typical distance signal for the harvester of FIG. 7.

FIG. 9 is a rear view of the harvester of FIG. 7 showing the headertilted to accommodate the slope.

FIGS. 10A and 10B are schematic representations of the harvester showingone calculation method for determining the expected distance (D2) to aforward location.

FIG. 11 is a flow chart illustrating an algorithm executed by theprocessor of FIG. 4 for controlling header height.

FIG. 12 is a flow chart for the header control loop for the processor inthe control system of FIG. 4 for lowering the header or performing smallheader lifts when predictive height control is actively operating.

FIG. 13 is a flow chart illustrating an algorithm executed by theprocessor of FIG. 4 for controlling header tilt.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to FIG. 1, therein is shown an agricultural harvester orcombine 10 comprising a main frame 12 having wheel structure 13including front and rear ground engaging wheels 14 and 15 supporting themain frame for forward movement over a field of crop to be harvested.Although wheels 14 and 15 are shown, the wheel structure 13 couldinclude or be composed of ground engaging tracks. Drive to the frontwheels 14 is provided through a conventional hydrostatic transmission byan engine mounted on the frame 12.

A vertically adjustable header or harvesting platform 16 is used forharvesting a crop and directing it to a feederhouse 18. The feederhouse18 is pivotally connected to the frame 12 and includes a conveyor forconveying the harvested crop to a beater 20. The beater 20 directs thecrop upwardly through an inlet transition section 22 to a rotarythreshing and separating assembly 24. Other orientations and types ofthreshing structures and other types of headers 16, such as transverseframe supporting individual row units, could also be utilized.

The rotary threshing and separating assembly 24 threshes and separatesthe harvested crop material. Grain and chaff fall through grates on thebottom of the assembly 24 to a cleaning system 26. The cleaning system26 removes the chaff and directs the clean grain to a clean grainelevator (not shown). The clean grain elevator deposits the clean grainin grain tank 28. The clean grain in the tank can be unloaded into agrain cart or truck by unloading auger 30.

Threshed and separated straw is discharged from the axial cropprocessing unit through outlet 32 to discharge beater 34. The dischargebeater in turn propels the straw out the rear of the combine. It shouldbe noted that the discharge beater 34 could also discharge crop materialother than grain directly to a straw chopper. The operation of thecombine is controlled from an operator's cab 35.

The rotary threshing and separating assembly 24 comprises a cylindricalrotor housing 36 and a rotor 37 located inside the housing 36. The frontpart of the rotor and the rotor housing define the infeed section 38.Downstream from the infeed section 38 are the threshing section 39, theseparating section 40 and the discharge section 41. The rotor 37 in theinfeed section 38 is provided with a conical rotor drum having helicalinfeed elements for engaging harvested crop material received from thebeater 20 and inlet transition section 22. Immediately downstream fromthe infeed section 38 is the threshing section 39. In the threshingsection 39 the rotor 37 comprises a cylindrical rotor drum having anumber of threshing elements for threshing the harvested crop materialreceived from the infeed section 38.

Downstream from the threshing section 39 is the separating section 40wherein the grain trapped in the threshed crop material is released andfalls through a floor grate in the rotor housing 36 to the cleaningsystem 28. The separating section merges into a discharge section 41where crop material other than grain is expelled from the rotarythreshing and separating assembly 24. Although the harvester 10 is shownas a combine 10 for harvesting grain, it is to be understood that thepresent invention may also be utilized with other types of harvestershaving vertically controlled headers.

The height of the header 16 is controlled by a hydraulic lift systemindicated generally at 60, and a header tilt system indicated generallyat 61 may also be provided to maintain the header generally parallel tothe surface of the ground. Feelers 62 or other conventional heightsensing devices such as acoustic sensors supported from transverselyspaced locations on the header 16 provide an indication of headerheight. A feederhouse transducer 64 provides an indication of the angleof the feederhouse 18 relative to the frame 12. The signals from thedevices 62 and 64 are connected via lines 62 a and 64 a (FIG. 4) to acontroller 66 which includes electrohydraulic valve structure 67 tocontrol hydraulic fluid flow to and from one or two lift cylinders 68connected between the feederhouse 18 and the frame 12 to operate thelift system 60 to maintain the header within a desirable operatingheight range. The valve structure 67 also controls extension andretraction of a tilt cylinder 69 to rotate the header 16 about afore-and-aft extending axis for operation parallel to the groundsurface. When the signal from one or more sensors 62 on one side of theaxis provides a raise indication while the signal from the opposite sideprovides a lower indication, the system will operate the cylinder 69 totilt the header about the axis for the proper attitude correction. Whensensors on both sides of the axis provide a raise or a lower indication,the cylinder 68 will be extended or retracted accordingly for thenecessary height correction to maintain the header in a preselectedrange of operating heights. Such a height control system is shown anddescribed in the aforementioned U.S. Pat. No. 4,776,153. The reactiontimes of the lift system 60 and the tilt system 61, however, are oftentoo slow to compensate for abrupt changes in the ground surface contour,particularly when the harvester 10 is operating at relatively highspeeds. The reaction time may also be too slow to compensate for suddenheader position changes relative to the ground that result from one ormore of the wheels 14 and 15 of the wheel structure 13 encountering adepression or raised area in the ground contour. The ability to cut acrop a preselected distance below the crop heads to limit throughput isalso limited.

An improved header height control includes a ground or crop contourpredictive system indicated generally at 70. The system 70 is mounted onthe combine 10 to provide ground contour information generally over theentire width of the path P of the header 16. The system 70 includes atransceiver 74 located at a central location on the cab 35 fortransmitting and receiving signals 76. The transceiver radiates signals76 t downwardly at an acute angle to the plane of the forward directionof the harvester 10 towards an area of ground 77 forwardly of theharvester 10. The signals 76 t are preferably scanned or radiated acrossthe entire width W of the path P of the header a distance on the orderof 10 to 20 meters forwardly of the cab 35. Reflected signals 76 r arereceived by the transceiver 74. The time interval between transmissionof a signal 76 t and the receipt of the signal 76 r provides anindication of the distance between the transceiver 74 and the reflectingportion 78 of the ground surface or crop surface. In turn, theindication of distance provides ground contour information.

As best seen in FIGS. 3A and 3B, the distance D increases with a drop inthe surface contour (D1 of FIG. 3a) and decreases with a rise in thecontour (D2 of FIG. 3b). Therefore, if an increasing distance D isdetected across an area 77, the controller 66 can initiate a lowering ofthe header 16 prior to the header and height sensing device 62 reachingthe area. If the distance D decreases across the area, indicating a risein the ground surface will soon be encountered by the header 16, thecontroller 66 can initiate header lifting. The system 70 is preferablyutilized to complement the operation of the height sensing device 62 onthe header 16 and initiate early reaction of the height control torapidly changing ground contours for reduced reaction time and decreasedlift power requirements. However, the system 70 can also be used forprimary control of header height if desired. For example, whencontrolling header position so crop cutting is maintained within apreselected range of distances below the crop heads, grounding is not aproblem and primary control is by the system 70.

The system 70 can also be utilized to complement the operation of thetilt system 61 to predict necessary header angle changes to avoidsituations wherein the header is substantially offset from a parallelrelationship with the ground. If the one side of the ground surface isrising relative to the opposite side for an area, advance information ofthe particular tilt necessary for that area can be provided for a timelytilt system response even at relatively high ground speeds.

The area scanned by the signals 76 includes areas 80 generally lying inthe path of the harvester wheel structure 13 so that, if desired, thecontour of the ground supporting the wheels 14 and 15 can be taken intoconsideration when the system is predicting the desired height controlresponse for the area 77. The system 70 includes a processor 86 forcalculating distances D based on signal travel time and converting thedistances to ground contour information. The contour information foreach area 77 is stored in memory to provide a ground contour historygenerally over a length of the path P extending from the present area 77receiving impinging signals 76 t rearwardly a distance at least equal tothe distance between the header 16 and the rear wheels 15. Therefore,the effect on header position due to changing ground contour under thewheel support structure 13 can be factored into the desired heightcontrol response for any given area 77. The processor 86 can calculatethe expected height response for a given area 77 on a time based historyof the contour areas or on a distance based history. For a distancebased history, harvester speed information is input to the processor vialine 90.

In one embodiment, the transceiver 74 transmits a signal 76 t that canpenetrate standing crop to reach the ground, such as a high frequencyradar beam. In another embodiment, a laser ranging device, such as aSICK model LMS 200 series laser measurement system, or a crop edgesensor (FIG. 5) mounted on a turntable 100, can be used for determininga crop surface contour which generally approximates the underlyingground surface contour. The crop edge sensor of FIG. 5 has a limitedscan angle of approximately 15 degrees for determining crop edge andproviding a guidance control signal on line 99. The turntable 100rotates the sensor about an upright axis to permit a full platform widthscan, which is on the order of 90 degrees, to be accomplished in severalsteps during time periods between guidance control signals. Thefrequency of the scans is preferably dependent on deviations of cropedge from a straight path with more scans being facilitated when thecrop edge is straight and fewer guidance corrections are required.

Referring to FIG. 6, a typical full platform width scan signal for thelaser crop edge sensor 74 of FIG. 5 is represented by the solid line at106. Distance, determined by the time for the signals 76 t to travel tothe area 77 and the corresponding reflected signals 77 r to be receivedat the transceiver 74, is plotted against scan angle for a typical scanof approximately 90 degrees. The portion 106 c represents the signalsreflected from the ground in area 108 outside the crop edge (CE). At thecrop edge CE there will be a sudden decease in the detected distance,represented by the segment 106 d, as the signal 76 t is reflected fromthe top of the crop at the crop edge rather than the ground. Thedistance d_(t) to the top of the crop across the width of the path W isrepresented by the segment 106 t. Theoretical ground contour (GC)therefore can be estimated by adding the distance change at the cropedge, represented by the length of the segment 106 d, to each distancemeasurement on the segment 106. The theoretical ground contour GC isprovided as an input to the height control system. If a transmitter witha crop-penetrating signal is utilized, the actual ground contour isdetected and the distance d_(t) will correspond to the line GC in FIG.6. If the position of the header 16 is to be controlled to cut crop apreselected distance below crop heads, the crop surface contourprediction is used by the controller 66.

FIGS. 7, 8 and 9 illustrate ground contour prediction to initiatereaction of the tilt system 61 in a timely manner to maintain generallyparallel relationship between the header and the surface of the ground.As seen in FIG. 8, the scan signal 106 shows a decreasing distance fromthe crop edge CE (the distance measured on the left side of the scan,D_(L), is greater than the distance D_(R) measured on the right side ofthe scan) to the opposite side of the header 16 which, in turn,indicates that the approaching area has a downward slope towards thecrop edge CE (FIG. 8). The processor 86 (FIG. 4) calculates header tiltnecessary for the radiated area and signals the electrohydrauliccontroller 67 to initiate actuation of the tilt cylinder 69 to assurethe header will have the proper tilt angle by the time the header 16reaches the area.

The angle of transmission of the signals 76 t relative to the horizontalcan be changed to increase or decrease the distance D (FIG. 2) betweenthe header 16 and the ground area being radiated as the ground speed ofthe harvester 10 increases or decreases. The angle is selected toprovide sufficient lead time for the lift and tilt control systems toreact to rapidly changing surface contours.

By way of example only, FIGS. 10A and 10B illustrate a calculationmethod model to estimate expected distance (D2) in an x-y coordinatesystem wherein four points P1-P4 are on a circle M of large radius R sothat the calculation can be linearized. Sensor position is (x₅, z₅), anda₅ is the inclination angle of the sensor. Feederhouse angle is zerowhen the header is on the ground. P1 is the point on the contour in thearea being radiated. P2 is a point on the header, and P3 and P4 arewheel contact points. Other conventional calculation methods can be usedfor ground and crop contour predictions based on signal travel time.

Referring to FIG. 11, after the predictive height control is initiatedat 200, the processor 86 determines distance D2 based on signal traveltime at 202. At 203, present feederhouse angle based on the signal fromthe feederhouse transducer 64 and present header height is determinedfrom the feederhouse signal and from signals from the height sensingdevices 62. The expected distance is calculated at 204 based on thefeederhouse angle and header height at 203. The measured distance D2 (at202) is compared with the expected distance (at 204), and if themeasured distance D2 is smaller than the expected distance (206),indicating that the contour is rising, the processor 86 signals thecontroller to lift the header 16 (208) with a time or distance baseddelay, if necessary, to coordinate the positioning of the header for theparticular area in the path with the arrival of the header at that area.If the header height is within the desired range of heights (206) orafter the lift is initiated at 208, the cycle is begun again as theprocessor returns to the step 202.

A control loop shown in FIG. 12 provides header lowering and small liftsof the header based on header height signals from the height sensingdevices 62 on the header and on the feederhouse angle signal. Actualheader height (HH) based on the signals from the devices 62 and thetransducer 64 is compared at 210 with a desired header height range HH*.If the desired header height HH* is less than the measured HH, theprocessor 86 signals the valve structure 67 to extend the cylinders 68and raise the header 16. If header height is below the desired range ofheights at 212, the cylinders 68 are retracted to lower the header 16.Header height is maintained (214) when the header height is in thedesired range. In the predictive control loop of FIG. 11, if the header16 is being lifted at 208 because of a predicted contour change in anarea, the processor ignores signals from the header sensors 62 to lowerthe header in order to avoid sudden reversals of the lift system and toassure adequate system response time to avoid problems such as groundingor cutting of the crop too far below the crop heads in the area.

Predictive header lowering usually is not required for operationswherein header height is maintained within an operating range of heightsrelative to the ground surface because of the fast lowering rate causedby the weight of the header. However, when the harvester is operating ina cut-below-crop head mode, it is usually advantageous for the operationto be purely predictive. When operating in such a mode, the control loopof FIG. 11 is modified to include an additional decision block toprovide a predictive lowering function at the “no” output branch ofblock 206. Before returning control to block 202, the distance D2 ischecked to see if it is larger than the expected distance, indicatingthe crop contour is dropping and a header lowering will be required tomaintain crop cutting in the desired range of distances below the crophead. The processor 86 signals the controller to lower the header 16with a time delay to coordinate the header lowering with the arrival ofthe header at the measured area. Since header lowering is much fasterthan header raising, the time delay for initiating lowering is typicallygreater than the time delay for initiating raising. Control is thenreturned to 202.

When the harvester 10 is equipped with a tilt system 61, control of thesystem is according to the flow chart shown in FIG. 13. Upon initiationof the predictive tilt control at 300, the distances D_(L) and D_(R) tothe left and right, respectively, of the centerline of the combine aremeasured at 302. The header tilt angle HT is measured at 303 by aconventional transducer (not shown) mounted on the feederhouse 18between the feederhouse frame and a front plate which mounts the header16. After HT is measured, the processor 86 calculates the expectedheader tilt HT_(exp) at 304 based on the value of HT found at 303 andcalculates the expected distances DL_(exp) and DR_(exp). If the measuredtilt HT is not within a preselected range of angles relative to theexpected tilt HT_(exp) (306), the distance D_(L) is compared with thedistance DL_(exp) at 308. If the distance D_(L) is less than DL_(exp),which indicates the left side of the header 16 will need to be raisedfor the approaching area, the processor 86 signals the electrohydrauliccontroller 67 to initiate actuation of the tilt cylinder 69 to lift theleft side of the header (310). If the distance D_(L) is greater thanDL_(exp), which indicates the left side of the header 16 is too high,the processor 86 signals the controller 67 to initiate tilt cylinderoperation to lower the left side of the header (312). If the measured HTis in the desired range (306) or after the necessary tilt correction hasbeen initiated (310 or 312), the processor returns to the step 302.Preferably, the conventional tilt control using the transversely spacedheader-mounted sensors 62 remains operational and is responsible forminor corrections to header tilt angle.

When the harvester 10 is operating in standing crops and the system isset to cut crop a preselected range of distances below the crop heads,the system is preferably operated in the predictive mode without needfor the conventional header-mounted sensors, and predictive headerlowering is enabled in the control loop of FIG. 11 as described above.Also, the delay between the contour prediction and the operation of thelift and tilt cylinders preferably is speed dependent (location based)for accuracy rather than dependant on time only.

Having described the preferred embodiment, it will become apparent thatvarious modifications can be made without departing from the scope ofthe invention as defined in the accompanying claims.

We claim:
 1. A method of controlling position of a harvester header tomaintain the header within a preselected operating height range, theheader having a preselected width and adjustably supported on a frame ofa harvester for positioning by hydraulic motor structure, the framesupported by ground wheel structure for traversing a field having aground surface contour, the method comprising: detecting contour of acrop area at a location offset forwardly of the header; and utilizingthe detected contour to automatically control the hydraulic motorstructure to initiate a header movement, prior to the header reachingthe crop area, to facilitate positioning of the header for operatingwithin a range of positions in the crop area, thereby improving responseof the header and reducing incidences of improper header positionresulting from rapidly changing contours.
 2. The method as set forth inclaim 1 wherein the step of detecting includes supporting a transmitterat a transmitter location offset from the header and independent ofheader positioning changes.
 3. The method as set forth in claim 2including the step of detecting a change of distance from thetransmitter location to the area, wherein the step of utilizing thedetected contour includes initiating a lowering of the header when thedetected change of distance indicates an increasing distance andinitiating a raising of the header when the detected change of distanceindicates a decreasing distance.
 4. The method as set forth in claim 1wherein the step of utilizing the detected contour includes determiningground contour on which the ground wheel structure will be supportedwhen the header is operating in the area.
 5. The method as set forth inclaim 1 wherein the step of detecting contour of a crop area includesdetermining crop top locations, and further including the step ofpositioning the header for operating at a height within a preselectedrange of distances below the crop top locations to thereby controlharvester throughput.
 6. The method as set forth in claim 1 wherein thestep of detecting contour includes radiating signals towards an area ofground having a width generally corresponding to the preselected widthand receiving reflected signals from the area to provide an indicationof ground surface contour over substantially the entire width of theheader.
 7. A method of controlling position of a harvester header tomaintain the header within a preselected operating height range, theheader adjustably supported on a frame of a harvester for positioning bymotor structure, the frame supported by ground wheel structure fortraversing a field having a ground surface contour, the methodcomprising: detecting contour of a crop area at a location offsetforwardly of the header; utilizing the detected contour for controllingthe motor structure to initiate header movement prior to the headerreaching the crop area and facilitate positioning of the header foroperating within a range of positions in the crop area, wherein the stepof utilizing the detected contour improves response of the header andreduces incidences of improper header position resulting from rapidlychanging contours; and wherein the step of utilizing the detectedcontour includes initiating a header tilt movement to facilitatemovement of the header to a position generally parallel to the ground inthe area prior to the header reaching the area.
 8. A harvester having aframe supported on the surface of the ground by wheel structure forforward movement through a field of crop with changing ground contour, aheader of preselected width supported for movement relative to the frameto maintain a generally constant position of the header relative to theground, a header control system for automatically moving the header asthe ground contour changes, and a ground contour detection systemconnected to the header control system, the ground contour detectionsystem including: a transmitter radiating a signal towards an areaforwardly of the header; a detector receiving reflected signals from thearea and providing an indication of the ground contour in the area priorto the header reaching the area; and wherein the header control systemis responsive to the indication of ground contour to facilitateautomatic movement of the header towards a preselected position for thearea prior to the header reaching the area so that a predictive andpower-reducing response of the lift system to rapid changes in groundcontour is facilitated.
 9. The harvester as set forth in claim 8 whereinthe signal is radiated over a width corresponding generally to the widthof the crop being harvested so that the indication of ground contourcorresponds to at least approximately the harvesting width.
 10. Theharvester as set forth in claim 9 wherein the transmitter comprises acrop edge detection transmitter.
 11. The harvester as set forth in claim8 wherein the ground contour detection system includes a processorproviding a surface contour history of ground surface forwardly of theheader and compensating for time delay between the ground contourindication and arrival of the header at the area.
 12. The harvester asset forth in claim 8 including a position transducer connected to theheader and providing a header height signal, and wherein the headercontrol system is also responsive to the header height signal.
 13. Theharvester as set forth in claim 8 wherein the transmitter is supportedfrom the frame above the header at a location independent of thevertical movement of the header.
 14. The harvester as set forth in claim13 wherein the indication of ground contour is a function of thedistance the reflected signals travel, and wherein the lift system isresponsive to an increasing distance of travel of the reflected signalsto facilitate lowering of at least a portion of the header that willtraverse an area from which the signals of increasing travel distanceare reflected, the lift system responsive to a decreasing distance oftravel of the reflected signals to facilitate raising of at least aportion of the header that will traverse an area from which the signalsof increasing travel distance are reflected.
 15. A harvester having aframe supported on the surface of the ground by wheel structure forforward movement through a field of crop with changing ground contour, aheader of preselected width supported for vertical movement relative tothe frame for harvesting the crop generally across the width of theheader, the crop to be harvested lying in a path to be traversed by theheader, and a header control system for automatically adjusting theheader vertically as the ground contour changes to maintain the headerwithin a range of heights for efficient harvesting and prevention ofgrounding of the header, the header control system including: atransmitter radiating signals towards an area on the path forwardly ofthe header over a width generally corresponding to the preselectedwidth; a detector receiving reflected signals from the path andproviding an indication of the ground contour over a substantial portionof the width of the path; and a header lift system connected to theheader and responsive to the indication of ground contour toautomatically initiate movement of the header towards a position withina desired range of heights for the location on the path before theheader reaches the location.
 16. The harvester as set forth in claim 15including a height sensor connected to the header and to the liftsystem, the height sensor providing a header height indication, andwherein the lift system is also responsive to the header heightindication.
 17. The harvester as set forth in claim 15 wherein thesubstantial portion of the width includes an area of ground in a pathengaged by the wheel structure as the harvester moves forwardly, andwherein the header lift system movement is dependent on the groundcontour in the path to compensate for anticipated changes in position ofthe frame resulting from movement of the wheel structure over the areaof ground.
 18. In a harvester having a frame supported on the surface ofthe ground by wheel structure for forward movement through a field ofcrop with changing ground contour and crop height contour, a headersupported for vertical movement relative to the frame for harvesting thecrop generally across a preselected operating width, and a headercontrol system for automatically adjusting the header vertically as thecontours change to thereby maintain the header within a range ofpositions for efficient harvesting and prevention of grounding of theheader, the header control system including: a transmitter radiatingsignals towards a location on the path forwardly of the header over awidth generally corresponding to the preselected width; a detectorreceiving reflected signals from the path and providing an indication ofat least one of the contours over a substantial portion of the entirewidth of the path; and a header positioning system connected to theheader and responsive to the indication to automatically initiatemovement of the header towards a position within a desired range for thelocation on the path before the header reaches the location.
 19. Theharvester as set forth in claim 18 including a height sensor connectedto the header and providing a header height indication, and wherein thelift system is also responsive to the header height indication.
 20. Theharvester as set forth in claim 18 wherein the transmitter radiatessignals that penetrate the crop and are reflected from ground surfacelocations in the path.
 21. The harvester as set forth in claim 18wherein the transmitter radiates signals that are reflected from thetops of plants in the path and the indication ground surface contour isestimated from the signals that are reflected form the tops of theplants.
 22. The harvester as set forth in claim 18 wherein the headerpositioning system includes a header tilt control, and wherein a tiltcontrol signal is provided to the header positioning system prior to theheader reaching the position to initiate a ground-following tiltmovement of the header.
 23. The harvester as set forth in claim 18wherein the transmitter comprises a crop edge detection transmitter, andwherein the detector also provides a crop edge signal for harvesterguidance control.
 24. The harvester as set forth in claim 23 wherein thetransmitter has scan angle substantially less than scan angle requiredto scan the signals over the preselected width, and further comprisingrotating structure operable to rotate the crop edge detectiontransmitter to scan the signals over the preselected width.
 25. Theharvester as set forth in claim 24 wherein the rotating structure isoperated during periods wherein crop edge signal is not provided forguidance control.
 26. The harvester as set forth in claim 18 whereincrop height contour is detected and wherein the desired range is a rangeof distances from the crop heads.